Variable condenser



W. DUBILIER VARIABLE coNDENsER Oct. 18, 1927.

Filed Feb. 14, 1924 Patented Oct. 18, 1927.

UNITED STATES PATENT OFFICE.

WILLIAM DUBILIER, OF NEW YORK, N. Y., ASSIGNOR TO DUBILIEB CONDENSERCORPORATION, A. CORPORATION OF DELAWARE.

VARIABLE CONDENSED.

Application led February 14, 1924. Serial No. 699,868.

My invention relates to condensers, and more particularly to variablecondensers.

An object of my invention is to provide a condenser structure in whichthe adjustments of capacity may be made with a minimum of wear and tearon the condenser elements.

Another object of my invention is to provide a condenser in whichadjustments may 0 be made with a minimum of friction of the operatingparts.

Heretofore, adjustment of capacity in condensers has usually beeneffected by bodily moving one of the condenser elements in relationshipto another condenser element. In some cases, it has been necessary todistort the movable condenser element, and in such instances, continuedlong use may result in deterioration of the movable element. In 2 thetype of condenser where the movable element is not distorted but isbodily moved, mechanism for keeping the movable element properly alignedwith the fixed element in all adjustments of the condenser has renderedthe condenser liable to derangement and short circuits.

- It is to overcome these diiiculties existing in prior art structuresthat this invention was conceived. With these and other objects in viewwhich may be incident to my improvements, the invention consists in theparts and combinations to be hereinafter set forth and claimed, with theunderstanding that the several necessary elements comprising myinvention, may be varied in oonstruction, proportions and arrangement,without departing from the spirit and scope of the appended claims.

In order to make my invention more clearly understood, I have shown inthe accompanying drawings means for carrying the same into practicaleiect, without limiting the improvements in their useful applications tothe particular constructions, which for the pur ose of explanation, havebeen made the subject of illustration.

Figure 1 is a vertical sectional view taken through the center of thedevice;

Fig. 2 is a view with a part of the side wall of the casing of thecondenser broken away, looking in the direction indicated by the arrowsin line 2 2 of Fig. 1;

Fig. 3 is a top plan view.

My condenser comprises an insulating casing, upon the floor of which areplaced the elements of the condenser which, in the present instance,consist of sheets of mica interleaved with metal foil. Above theelements of the condenser, lies a com ression member having a slopedupper sur ace operating as a cam surface. Adapted to travel over the camsurface is a roller, which is swung with the rotative movement impartedto a central shaft through a turning knob. To insure that the rollershall be swung in substantially the same plane without undue stress onthe central shaft, the top of the casing is provided with a ball race,and a bearing support piece has a similar ball race in its uppersurface. The bearing support piece is adapted to rotate parallel to theu per wall of the casing, being held in space relationship from theupper wall by means of ball bearings.

The roller bears against this bearing support, and the longitudinalstrain on the central shaft is relieved thereby. There is a spring meansoperating against the compression member, tending to relieve the strainon the stack of flexible elements. The adjustment of capacity is e'ectedby swinging the roller to compress the compression plate against thefiexible elements of the condenser. The capacity of the device will varyin accordance with the amount of compression to which the iexiblecondenser elements are subjected.

Referring to the drawings for a more detailed description, I have showna condenser casing comprising an annular side wall 1, and a bottom wall2. The Casin may be made of insulating material, but t is is notnecessary as provision is made t0 insulate the condenser elements fromthe casing. A disk 3 of material similar to that of the casing forms thetop wall, and is provided with screw-threads 4 which engage withscrewthreads formed on the upper interior of the side wall 1. Byscrewing down the upper or top wall 3 into the side Wall 1, a verycompact, neat casing is formed. The bottom wall 2 is provided with anannular centrally located inwardly projecting protuberance 5. Projectingthrough an aperture centrally formed in the protuberanoe 5, is the endof a centrally located shaft 6, which may be made of metal. The upperend of the shaft 6 projects through a centrally located aperture 7formed in the upper wall 3 of .the

casing. An operating knob 8, which is keyed to the shaft 6 by means of apin 9, is adapted to rotate the shaft 6 to accomplish the setting of thecondenser, as will be later described.

Resting on the floor of the condenser, is a flexible disk 10 of mica,which comprises one of the insulating disks of the condenser. The disk10 is provided with a central aperture 11 which fits around theprotuberance 5 formed in the lower wall 2 of the casing. There is aconsiderable clearance between the outer periphery of the protuberance 5and the edge of the aperture 11 which, to an extent, insures that thedisk 10 will not come into abrasive contact with the centralprotuberance 5. The disk 10 is preferably attached to the bottom wall 2of the casing by some suitable adhesive. Lying on the insulating micadisk 1() is an 'annular strip of metallic foil 12, provided with acentral aperture 13 somewhat larger than the centfl aperture 11 of themica sheet 10. The annular sheet 12 of metallic foil is of lesserdiameter than the insulating sheet 1() so that the sheet 10 overlaps thefoil 12 at the inner and the outer edges. Mounted over the foil 12 is aninsulating sheet of mica 14, of shape and dimensions similar to theinsulating sheet 10. Mounted above the insulating mica sheet 14 is anannular` foil member 15 of similar construction to the foil member 12.vThis condenser stack comprising flexible elements laid one on top ofanother, consists of insulating sheets of mica corres onding to the micasheet 10, which I have esignated by the numerals 16, 18 and 20, andbetween the mica sheets 16 and 18, and the mica sheets 18 and 20, aresheets of metallic foil 17 and 19 respectively, corresponding to thestrip of metallic foil 12. This whole stack of flexible condenserelements may be held together by some suitable gum or adhesive.

It will be understood that a condenser pile built of interleavedflexible insulating sheets of mica and sheets of metallic foil is as awhole flexible and compressible. In a stack of flexible elements soformed there is a considerable degree of compressibility, and by reasonof the inherent resilience of the material of which the stack is formed,upon release of pressure the stack tends to assume its formerdimensions.

In other words, a stack so formed will compress under pressure andexpand upon release of pressure, thus giving a variation in the totalcapacity of the device, since the capacity varies inversely as thedistance between the plates. It is also true that the dielectricexisting between the metallic plates of the condenser comprises air andmica. When the condenser stack is under greatest pressure and the platesare the -closest together, more air is excluded from the actual value ofK. C equals K where C is the capacity; A is the inside area of theplates; d is the distance between the plates; and K is the actualdielectric Constant, which will vary between l, the dielectric constantfor air` and 8 the maximum dielectric constant for mica.

Sheets of metallic foil 12 and 17 are provided with extending tabs 21and 22, respectively, through which fits a binding post 23, whose headcompresses a washer 24 against the tabs 21 and 22 and makes electricalconnection therewith. The binding post 23 fits through an insulatingbushing 25 passing through an aperture formed in the lower wall 2 of thecasing. A nut 26 is tightened on the protruding end of the bindlng post23 and holds the binding post in place, pressing on an insulating washer27 which contacts against the lower wall 2. Another nut 28 screwed ontothe end of the binding post 23 is adapted to compress a terminal 29against the nut 26.

The metallic foil members 19 and 15 are provided with extension tabs 31and 32, respectively, through which passes a binding post 33, Whose headcontacts with a holding washer 34, to hold the tabs 31 and 32 rmly inelectrical connection with the binding post. The binding post 33 passesthrough an insulating bushing 35 extending through the bottom Wall 2 ofthe casing. A holding nut 36 holds the binding post firmly in place, andbears against an insulating holding washer 37 which contacts with thewall 2 of the casing. A terminal 38 is adapted to be held between thenut 36 and another nut 39 on the binding post 33. Thus, electricalconnection may be made from the outside with the flexible metallicplates of the condenser stack, the whole of which is formed of flexibleelements. By reason of the fact that the condenser elements and theconnections are insulated from the casing, it is notl necessary to havethe casing formed of insulating material, though it may so be formed.

Adapted to bear on the upper mica sheet 20 of the condenser stack is acompression member 4 1, which may or may not be formed of insulatinmaterial, and is hinged at 42 to a hinge pin 43 that extends into thewalls of the casing, as can be plainl seen in Fig. 3. On the oppositeside of t e compiession member 41 from its hinged attachment to the sidewall of the casing, is a compression spring 44, whose lower end rests inan annular depression 45 formed in the upper inner side of the lowerwall 2 of the casing.

At its upper end, the spring rests in an annular depression 46 formed inthe lower side of the compression member 41. The compression spring 44constantly tends to raise the compression member 41 and release thepressure. An enlarged central aperture 47 is formed in the compressionmember, through which passes the shaft 6. The aperture 47 is purposelymade of sufficient size so that the compression member 41 may be swungon its hinge over an appreciable arc without contacting with the centralshaft 6.

The upper surface 48 of the compression member 41 has a slope which Ihave indicated in Fig. 2 as taking the form of a spiral or volute,though the particular shape of surface may be varied. This surface 48acts as a cam surface, and upon it is adapted to roll a roller orwedging member 49 mounted on a shaft 51, whose inner end 52 isscrew-threaded into the shaft 6. The head 53 of the shaft 51 fits intoan aperture 54 formed in the outer end of the roller 49, and preventsthe roller from longitudinal movement on the shaft 5l.

By moving the operating handle 8, the roller 49 may be swung in ahorizontal plane, and its surface will pass over the sloped cam surface48 of the compression member 41. The compression member 41 will take aposition, therefore, depending on the position of the roller 49.

To prevent the roller 49, as well as the shaft 51 and the shaft 6 frombeing subjected to too great strain, there is mounted above the roller49 a bearing support disk 55 having a ball race 56 therein. A ball race57 is formed in the lower side of the top wall 3 of the casing, andballs 58 travel in these adjacent ball races. The bearing support disk55 takes the upward pressure on the roller in its rolling contact withthe sloped surface 48 of the compression member 41. By reason of thefact that the bearing support disk 55 travels on ball bearings,

the roller 49 is not prevented from freely rolling on the upper surface48 of the compression member.

In operation, by revolving,r the handle 8, the roller 49 will travelover the sloped surface 48 of the compression member 41. The compressionmember 41 is caused to compress the stack of flexible condenser elementsin one direction of rotation, which in the present instance would becounter-clockwise, and

mum of wear and tear on the elements of 9 the condenser, since none ofthe elements are subfected to abrasion in changing from one setting ofthe condenser to another setting. The parts of the condenser are few,and the construction strong and durable. While delicate and minutesettings may be accomplished, the means for effecting the capacity.changes is not delicate or easily subject to iniury.

I may so adjust the factor of friction between the various moving parts,that it will be an easy matter to make the capacity adjustments, yet theforce exerted on the roller by the cam surface when the condenser platesare under compression, will not be sufficient to cause the condenser toautomaticallv reset itself.

Though I have shown the compression member as hinged to the side of thecasing, it is to be understood that it is not necessarily attached andmay freely float within the casing.

While I have shown and described the preferred embodiment of myinvention, I wish it to be understood that I do not confine myself tothe precise details of constriiction herein set forth by way ofillustration, as it is apparent that many chanves and variations may bemade therein, tby those skilled in the art, without departing from thespirit of the invention, or exceeding the scope of the appended claims.

I claim 1. A variable condenser comprising flexible elements insuperposed relationship, a compression member adapted to bear on theflexible elements, and a wedging member operating to vary the pressureof the compression member on said elements, the coinpression memberhaving a cam surface to be engaged by the wedging member.

2. A variable condenser comprising fiexible elements in superposedrelationship, a support on which the flexible elements rest, acompression member adapted to bear on the elements, said member having acam surface, and a wedging member adapted to bear on the surface of thecompression memberl to vary the pressure on the elements.

3. A variable condenser comprising flexible elements in superposedrelationship, a pivoted compression member adapted to bear on theflexible elements, and a wedging member operating to vary the pressureof the compression member on said elements, the compression member havina cam surface to be engaged by the wedglng member.

4. A variable condenser comprising flexible elements in superposedrelationship, a support on which the flexible elements rest, a pivotedcompression member, and means to vary the pressure of the compressionmember on the elements, said member having a cam surface to be engagedby said means.

5. A variable condenser comprising flexible elements in superposedrelationship, a supporton which the flexible elements rest, a pivotedcompression member adapted to bear on the elements, said member having acam surface, and a wedging member adapted to bear on the surface of thecompression member to vary the pressure on the elements.

6. A variable condenser comprising superposed flexible elements, acompression member having a sloped upper surface, a roller bearing onthe sloped upper surface, and means to cause relative movement betweenthe upper surface and the roller to vary the pressure on the elements.

7. A variable condenser comprising superposed elements in Contact witheach other, a compression member having a sloped surface, a rollerbearing on said surface, and means to move the roller over the surfacet0 vary the pressure on the elements.

8. A variable condenser comprising superposed flexible elements incontact with each other, a support on which the elements rest, a pivotedpressure member bearing on the elements and having a sloped surface, aroller bearing on said surface, and means to move the roller over thesurface to vary the pressure on the elements.

9. A variable condenser comprising su rposed elements in contact witheach ot er,

a compression member having a sloped surface, a roller bearing on saidsurface, and a shaft for swinging the roller, whereby the elements aresubjected to varying pressure.

10. A variableA condenser comprising a casing, superposed flexibleelements in contact with each other on the floor of the casing, acompression member having a sloped surface and pivoted on the wall ofthe casing, a roller bearing on the upper surface, a shaft for swingingthe roller, and means cooperating with the upper wall of the casing totake the strain transmitted to the roller.

11. A variable condenser comprising a casing, superposed flexibleelements in contact with each other on the floor of the casing, acompression member having a sloped surface, a roller bearing on theupper surface, a shaft for swinging the roller, and a bearingsupportagainst which the roller bears.

12. A variable condenser comprising a casing, superposed flexibleelements in contact with each other on the floor of the casing, acompression member having a sloped surface, a roller bearing on thesloped surfacea shaft for swinging the roller, an upper wall of thecasing, a bearing support, and ball bearings between the bearing supportand the upper wall of the casing.

13. A variable condenser comprising a casing having upper, lower andside walls, superposed flexible elements in contact with each other onthe lower wall of the casing, a compression member having` a slopedsurface and pivoted on the side wall of the casing, a roller bearing onthe sloped surface, a shaft for swinging the roller, a bearing support,ball bearings between the bearing support and the upper wall of thecasing, and a spring cooperating with the compression member tending toconstantly return the condenser to its minimum setting.

In testimony whereof I aix my signature.

WILLIAM DUBILIER

